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Answer:

The coupling constant for the quartet of CHO protons equals JCH,CH3 = 2,7 Hz (2,84 Hz).
Reasoning: Separation of two neighboring lines of the quartet in a 300 MHz spectrometer: 0.009 ppm,
therefore JCH,CH3 = (0,009 10-6 300 106 Hz) = 2,7 Hz
Compare these results to the methyl proton doublet of the ether
(CH3)2CH-O-CH(CH3)2!

Now continue to the solutions of the line-shape problems.